Effect of Tc-99m elution in vivo from red cells on red cell volumes measured using autologous Tc-99m-labeled red cells: comparison with Cr-51 method

The purpose of this work was to compare the measured red-cell volume (RCV) using sodium pertechnetate [RCV-Tc-99m] compared to the reference technique using sodium radiochromate [RCV-Cr-51] and to assess the influence of technetium-99 elution on the RCV-Tc-99m value. Ten patients had simultaneous measurements of RCV-Tc-99m and RCV-Cr-51. Elution of Tc-99m from red blood cells was 2.9% and led to an average overestimation of RCV-Tc-99m of 3.7%. The introduction of individual tracer elution rates in the RCV-Tc-99m calculation corrects this overestimation.